Secondary Cooling: Influence of Process Parameters and Laboratory Heat Transfer Measurements

In secondary cooling, it is very important to know the cooling heat-flux for the actual spray cooling situation with respect to various parameters like the local position, the nozzle types and distances, and the water and air flow rates, in order to be able to control the cooling conditions precisely. Since heat-flux measurements on a casting machine are too challenging, experimental laboratory test rigs have been designed and used for measurements by different research groups. In these experiments, metal probes of different dimensions and materials are heated up to the desired temperature (around 900 to 1200 °C) and then exposed to spray nozzles. The heat-flux is usually measured by temperature sensors immersed in the probe body, and the heat flux is then determined from the measured temperature by using inverse modelling methods. In this contribution, the differences between the real and laboratory conditions are focused using a mathematical heat transfer simulation model. The influence of strand surface temperature, nozzle spray water flow conditions (water retention during draining) and Leidenfrost effect are pointed out. Simulations of measured heat-fluxes for different virtual setups are compared.